Marine Astrolabes
Filipe Castro, Nicholas Budsberg, and James Jobling
Introduction
Probably developed in Roman Egypt and later simplified and adapted by the Portuguese to measure the height of the Sun above the horizon in the late 15th century, marine astrolabes are part of the intellectual revolution of the Renaissance and are linked to the European maritime expansion.
Marine astrolabes were used together with tables that gave the position of the sun on every day of the year at any latitude.
Marine astrolabes deserved scholarly attention since the beginning of the 20th century. A first inventory of 10 known marine astrolabes was published by David Waters in 1957, and a second, by the same author, in 1966, describing 21 specimens.